Dynamic reference method and system for interventional procedures

ABSTRACT

An interventional device configured for placement in or near an internal organ or tissue is provided. The interventional device includes a reference portion having three or more sensor elements. In one implementation, the interventional device and associated sensor elements provide dynamic referencing of the internal organ, tissue or associated vasculature after registration of the sensor data with images and/or volumetric representations of the internal organ or tissue.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 11/906,445, entitled “Dynamic Reference Method andSystem for Interventional Procedures,” filed Oct. 2, 2007, which isherein incorporated by reference in its entirety for all purposes.

BACKGROUND

The present technique relates generally to interventional procedures,such as interventional medical procedures. In particular, the presenttechnique relates to image-guided interventional techniques, such asthose used in conjunction with various radiology procedures.

As medical imaging technologies have matured, it has become possible tocombine the use of medical imaging techniques with the performance ofinvasive procedures. For example, interventional procedures such asbiopsies and tumor ablations may benefit from the use of imagingtechniques that allow a clinician to visualize the target region alongwith the intervention device while the procedure is being performed. Inthis way, the clinician may guide the interventional device to thetarget region with relative accuracy and, perhaps, without unnecessarytissue damage.

In practice, such image-guided interventional techniques typicallyemploy a tracking frame of reference device placed proximate to theanatomy of interest. The reference device moves with the patient toprovide accurate and consistent tracking of the anatomy of interest.Typically, the reference device needs to be rigidly secured to theanatomy of interest. As a result, the reference device is generallyattached to hard bone near the anatomy of interest. As a result, suchimage-guided interventional techniques are generally limited to regionsin the body bounded by bony anatomy, such as cranial neurosurgery,spine, orthopedic, and sinus procedures.

While such techniques are useful, clearly there are other areas of thebody that are not bounded by bony structures and that might also benefitfrom such image-guided techniques. However, regions of the body that arenot bounded by such bony structures, such as cardiac and abdominalregions, currently cannot benefit from such image-guided techniques dueto the inability to affix a reference device proximate to the anatomy ofinterest. Further, many internal organs that might benefit fromimage-guided interventional techniques can move, such as due torespiration, gravity, and so forth, and therefore, present additionalinterventional challenges. In addition, even in regions of the anatomywhere there is proximate bone, it may not be desirable to attach areference device to the bone. Therefore, it is desirable to provide areference technique for image-guided interventional procedures that doesnot require a reference device affixed to skeletal structures.

BRIEF DESCRIPTION

The present technique is generally directed to the dynamic referencingof an internal structure in an image-guide interventional procedure. Inone implementation, an interventional device having three or more sensorelements is provided. In such an embodiment, the interventional deviceis placed on or in an internal structure, such as an internal organ orvasculature, such as during an interventional procedure. Signals orfields generated by the sensor elements, such as electromagnetic signalsor fields, may be used to determine the positions of the sensorelements. The positions of the sensor elements may then be registeredwith a set of image based data which may or may not include image datarepresentative of the sensor elements. In one embodiment, theregistration occurs automatically. Once the signals generated by thesensor elements is registered with the images or volumetricrepresentations of the internal structure, the position and orientationinformation derived from the sensor elements may be used to modify oradjust the visual representation of the internal structure to reflectmotion or deformation of the structure. The modified or adjusted visualrepresentation may then be used to allow a surgeon or other clinician toperform an image-guided invasive procedure based on images reflectingthe current position and shape of the internal structure.

In accordance with one aspect of the present technique, a trackingsystem is provided. The tracking system includes an interventionaldevice. The interventional device includes a reference portionconfigured for placement proximate to or inside an internal organ. Thereference portion is not physically attached to the internal organ whenso placed. The interventional device also includes two or more sensorelements integrated on the reference portion. Each sensor element isconfigured to provide at least position information. Additionally, eachsensor element is sized differently or positioned so as to beidentifiable in a radiographic image. The tracking system also includesa controller configured to receive the position information generated bythe two or more sensor elements. The controller is also configured toregister the two or more sensor elements to the corresponding positioninformation in the radiographic image of the internal organ based atleast in part upon the size or position differences between the two ormore sensor elements.

In accordance with a further aspect of the present technique, a trackingsystem is provided. The tracking system includes an interventionaldevice. The interventional device includes a reference portionconfigured for placement proximate to or inside an internal organ. Thereference portion is not physically attached to the internal organ whenso placed. The interventional device also includes one or moremagnetoresistance sensors integrated with the reference portion. The oneor more magnetoresistance sensors generate at least position informationin response to an externally generated magnetic field. The trackingsystem also includes a controller configured to receive the positioninformation generated by the one or more magnetoresistance sensors. Thecontroller is also configured to register the one or moremagnetoresistance sensors to the corresponding position information in aradiographic image.

In accordance with an additional aspect of the present technique, atracking system is provided. The tracking system includes aninterventional device. The interventional device includes a referenceportion configured for placement proximate to or inside an internalorgan. The reference portion is not physically attached to the internalorgan when so placed. The interventional device also includes one ormore magnetoresistance sensors integrated on the reference portion. Theone or more magnetoresistance sensors are configured to generate a firstset of position data in response to an applied magnetic field. Thetracking system also a surgical tool including one or more additionalmagnetoresistance sensors integrated on the surgical tool. The one ormore additional magnetoresistance sensors are configured to generate asecond set of position data in response to the applied magnetic field.Additionally, the tracking system includes a controller configured toreceive the first and the second set of position data. The controller isalso configured to register the first and the second set of positiondata with a radiographic image of the internal organ.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 depicts an interventional device including sensor components, inaccordance with an embodiment of the present technique;

FIG. 2 depicts an interventional device inserted into an organ, inaccordance with an embodiment of the present technique;

FIG. 3 depicts a magnetoresistance sensor placed on a substrate, inaccordance with an embodiment of the present technique;

FIG. 4 depicts components of an imaging system and a positiondetermining system, in accordance with one embodiment of the presenttechnique;

FIG. 5 depicts components of an imaging system and a positiondetermining system, in accordance with a further embodiment of thepresent technique;

FIG. 6 depicts components of a computed tomography or three-dimensionalfluoroscopy imaging system and a position determining system, inaccordance with an embodiment of the present technique;

FIG. 7 depicts components of a computed tomography or three-dimensionalfluoroscopy imaging system and a position determining system, inaccordance with a further embodiment of the present technique;

FIG. 8 depicts examples of acts for using a position determining system,in accordance with an embodiment of the present technique; and

FIG. 9 depicts examples of acts for using a position determining system,in accordance with a further embodiment of the present technique.

DETAILED DESCRIPTION

The present technique is directed to dynamic referencing of internalorgans for image-guided interventional procedures. In particular, thepresent technique utilizes an interventional device configured with oneor more tracking devices. The interventional device is configured forplacement next to or in an internal organ of interest such that movementof the organ can be tracked in conjunction with acquired images or imagedata. In particular, in an embodiment, the movement of the trackingdevices is automatically registered with the image data, without the useof anatomical or fiducial markers. In this manner, an image-guidedinterventional procedure may be performed using the dynamic referenceinformation acquired using the interventional device. Because theinterventional device can be associated with the anatomy of interestwithout being affixed to bone, the present technique may be suitable foruse with percutaneous procedures performed on internal organs that maymove or be moved and which are not close to a suitable skeletal anchor.Examples of such organs include, but are not limited to the liver,lungs, kidneys, pancreas, bladder, and so forth.

For example, referring to FIG. 1, an interventional device 10 isdepicted that is suitable for placement near, in, or on an organ ofinterest. The interventional device 10 includes a reference portion 14.The reference portion 14 includes, in this example, three or more sensorelements 16 that, in one embodiment, may be used to acquire positioninformation relating to the reference portion 14. In other examples,depending on the type of sensor elements 16 employed, fewer sensorelements (i.e., one or two) may be employed. In the depicted embodiment,a conductive element 18 is also provided which may be suitable forproviding power to the sensor elements 16 in implementations in whichthe sensor elements are powered.

For example, in an embodiment, the interventional device 10 is acatheter 20. An example of such a catheter 20 might be a 7-frenchstraight catheter suitable for introduction via a jugular or femoralvein and for insertion of the tip, here depicted as reference portion14, into the hepatic (or other) vasculature, as depicted in FIG. 2. Insuch an embodiment, the catheter tip may be guided to the hepatic vein22 (or other vein) under fluoroscopy after introduction of a suitablecontrast agent to the blood stream. Once at the liver 24, the tip of thecatheter 20 can be lodged into the hepatic vein 22 such that thereference portion 14 is deep within the liver 24 and in a stableposition. In such an implementation, because the liver 24 movesessentially as a rigid body during respiration and because the referenceportion 14 is lodged within the hepatic vein 22, the reference portion14 will move with the liver 24. Because the reference portion 14 willmove with the liver 24, the reference portion 14 can act as a dynamicreference with regard to the liver 24. As a result, an interventionalprocedure, such as insertion of a biopsy needle 26 into a structure ofinterest 28 (e.g., a lesion), can be performed using image-guidedtechniques using position or motion information obtained using thesensor elements 16 integrated on the reference portion 14. Moreover, tofurther facilitate the interventional procedure, the biopsy needle 26,or other interventional tool, may include the sensor elements 16 toprovide position or motion information regarding the position and/ororientation of the biopsy needle (or other tool).

In certain implementations, the sensor elements 16 are not provided in alinear arrangement, i.e., the sensor elements 16 do not form a singleline, such that the respective sensor elements 16 can be distinguishedfrom one another based upon their known spatial relationships. Forexample, in the depicted embodiments of FIGS. 1 and 2, the sensorelements 16 are provided on a curved portion of the catheter 20 suchthat the information received from the sensor elements 16 can be used todistinguish the respective sensor elements 16 from one another based onknown spatial and/or geometric relationship of the sensor elements 16 toone another.

In one embodiment, the sensor elements 16 are provided aselectromagnetic (EM) microsensors, such as solid or hollow EM coils,that are integrated into or securely attached to the interventionaldevice 10. In implementations employing such EM coils, each EM sensorcoil can provide information regarding the orientation of the respectivecoil in two directions. In one embodiment, however, a single coil cannotprovide sufficient information to determine the roll of the respectivecoil since the coils are axisymmetric. Therefore, each coil, in such anembodiment, has five degrees of freedom. If at least two such coils arecombined into or integrated onto a device, such as the interventionaldevice 10, so that the coils have a known and fixed relationship to oneanother, then six degrees of freedom (x, y, z, roll, pitch, yaw) can bedetermined from the aggregate or combined information obtained form thetwo or more coils. In this way, the EM fields generated by the EM coilsmay be used to determine the position and orientation of the portion ofthe interventional device upon which they are integrated. For example,in the embodiment depicted in FIGS. 1 and 2, the sensor elements 16(which are presumed to be EM coils in this example) that are fixed onthe reference portion 14 of the catheter 20 allow the position andorientation of the reference portion 14 of the catheter 20 to bedetermined based upon the EM fields generated by the EM coils.

In another embodiment, the sensor elements 16 are provided asmagnetoresistance (MR) sensors 16, as illustrated in FIG. 3. In such anembodiment, the magnetoresistance sensor 16 provides a change inelectrical resistance of a conductor or semiconductor when an externalmagnetic field is applied. Additionally, each individualmagnetoresistance sensor 16 may be suitable for providing positioninformation (i.e., x, y, and z position data) and/or orientationinformation (i.e., roll, pitch, and yaw orientation data) in thepresence of an external magnetic field. Thus, the magnetoresistancesensor 16 operates with six degrees of freedom.[]

In certain embodiments, the magnetoresistance sensor 16 may include anarea array or peripheral array interconnect flip chip magnetoresistancesensor 16. The flip chip structure of the magnetoresistance sensor 16 iscoupled to a flexible or rigid substrate 30 (e.g. printed circuit board(PCB)) as well as connectors to external circuitry. The substrate 30 maybe suitable to be affixed to or within the interventional device 10and/or surgical tool (e.g., the biopsy needle 26). The electricalconnection may be provided on or in communication with pads of themagnetoresistance sensor 16 and corresponding pads on the substrate 30.The substrate 30 may include or be connected to one or more wires,traces, flex-circuits, or other conductive structures 34 that allow datato be read out from the magnetoresistance sensor 16. Themagnetoresistance sensor 16 may also include an underfill material 36(e.g., an epoxy) that may be applied to the magnetoresistance sensor 16to fill some or all of the open space between the magnetoresistancesensor 16 and the substrate 30, thereby providing additionalthermomechanical stability. Further, a mold cap 38 or other covering orprotective layer may be deposited or coated on the magnetoresistancesensor 16 to provide additional protection and/or stability.

As described above, an interventional device 10, whether equipped withelectromagnetic coils or magnetoresistance sensors, may be usedaccordance with the present technique to allow image-guided invasiveprocedures. As will be appreciated, any imaging modality suitable foruse in an image-guided interventional procedure may be employed in thepresent technique. Examples of such imaging modalities include X-raybased imaging techniques which utilize the differential attenuation ofX-rays to generate images (such as three-dimensional fluoroscopy,computed tomography (CT), tomosynthesis techniques, and other X-raybased imaging technologies). Other exemplary imaging modalities suitablefor image-guided interventional procedures may include magneticresonance imaging (MRI), ultrasound or thermoacoustic imagingtechniques, and/or optical imaging techniques Likewise, nuclear medicineimaging techniques (such as positron emission tomography (PET) or singlepositron emission computed tomography (SPECT)) that utilizeradiopharmaceuticals may also be suitable imaging technologies forperforming image-guided interventional procedures. Likewise, combinedimaging modality systems, such as PET/CT systems, may also be suitablefor performing image-guided interventional procedures as describedherein. Therefore, throughout the present discussion, it should be bornein mind that the present techniques are generally independent of thesystem or modality used to acquire the image data. That is, thetechnique may operate on stored raw, processed or partially processedimage data from any suitable source.

For example, turning now to FIG. 4, an overview of an exemplarygeneralized imaging system 40, which may be representative of variousimaging modalities, is depicted. The generalized imaging system 40typically includes some type of imager 42 which detects signals andconverts the signals to useful data. As described more fully below, theimager 42 may operate in accordance with various physical principles forcreating the image data. In general, however, image data indicative ofregions of interest in a patient 44 are created by the imager 42 in adigital medium for use in image-guided interventional procedures.

The imager 42 may be operated by system control circuitry 46 whichcontrols various aspects of the imager operation and acquisition andprocessing of the image data as well as dynamic reference data acquiredusing the present techniques. In the depicted generalized embodiment,the system control circuitry 46 includes movement and control circuitry48 useful in operating the imager 42. For example, the movement andcontrol circuitry 48 may include radiation source control circuits,timing circuits, circuits for coordinating the relative motion of theimager 42 (such as with regard to a patient support and/or detectorassembly), and so forth. The imager 42, following acquisition of theimage data or signals, may process the signals, such as for conversionto digital values, and forwards the image data to data acquisitioncircuitry 50. For digital systems, the data acquisition circuitry 50 mayperform a wide range of initial processing functions, such as adjustmentof digital dynamic ranges, smoothing or sharpening of data, as well ascompiling of data streams and files, where desired. The data are thentransferred to data processing circuitry 52 where additional processingand analysis are performed. For the various digital imaging systemsavailable, the data processing circuitry 52 may perform substantialreconstruction and/or analyses of data, ordering of data, sharpening,smoothing, feature recognition, and so forth.

In addition to processing the image data, the processing circuitry 52may also receive and process motion or location information related toan anatomical region of interest, such as the depicted internal organ 54and/or lesion 28. In the depicted embodiment, an interventional device10 is placed on or near the internal organ 54 (here depicted as theliver 24 of the patient 44). The interventional device 10 and/or thesurgical tool 26, as discussed above, may each be provided with various(for example, one or more) sensor elements 16 (see FIGS. 1 and 2)configured to provide position information. In one embodiment, thesensor elements 16 are EM coils each configured to generate adistinctive and distinguishable EM field. In other embodiments, thesensor elements 16 are one or more magnetoresistance sensors thatgenerate position and/or orientation data in response to an externalmagnetic field. In certain embodiments where the sensor elements 16 arepowered, the sensor elements 16 may be connected, such as via one ormore conductive wires 56 running through the catheter, to suitable powercircuitry 58, such as an electrical power source or outlet or a suitablebattery. While in the depicted embodiment the power circuitry 58 isdepicted as being separate from the system control circuitry 46, inother embodiments the power circuitry 58 may be part of the systemcontrol circuitry 46.

In the depicted embodiment, the signals or fields generated by thesensor elements 16 are detected by one or more antennas 60. The detectedlocation information is provided to or acquired by receiver circuitry 62which in turn provides the location data to the processing circuitry 46.As discussed in greater detail below, the location data may be used inconjunction with the image data to facilitate an image-guided procedure.

The processed image data and/or location data may be forward to displaycircuitry 63 for display at a monitor 64 for viewing and analysis. Whileoperations may be performed on the image data prior to viewing, themonitor 64 is at some point useful for viewing reconstructed imagesderived from the image data collected. The images may also be stored inshort or long-term storage devices which may be local to the imagingsystem 40, such as within the system control circuitry 46, or remotefrom the imaging system 40, such as in picture archiving communicationsystems. The image data can also be transferred to remote locations,such as via a network.

For simplicity, certain of the circuitry discussed above, such as themovement and control circuitry 48, the data acquisition circuitry 50,the processing circuitry 46, and the display circuitry 63, are depictedand discussed as being part of the system control circuitry 46. Such adepiction and discussion is for the purpose of illustration only,however, and is intended to merely exemplify one possible arrangement ofthis circuitry in a manner that is readily understandable. In otherembodiments the depicted circuitry may be provided in differentarrangements and/or locations. For example, certain circuits may beprovided in different processor-based systems or workstations or asintegral to different structures, such as imaging workstations, systemcontrol panels, and so forth, which functionally communicate toaccomplish the techniques described herein.

The operation of the imaging system 40 may be controlled by an operatorvia a user interface 65 which may include various user input device,such as a mouse, keyboard, touch screen, and so forth. Such a userinterface may be configured to provide inputs and commands to the systemcontrol circuitry 46, as depicted. Moreover, it should also be notedthat more than a single user interface 65 may be provided. Accordingly,an imaging scanner or station may include an interface which permitsregulation of the parameters involved in the image data acquisitionprocedure, whereas a different user interface may be provided formanipulating, enhancing, and viewing resulting reconstructed images.

As noted above, the sensor elements 16 may also be provided asmagnetoresistance sensors 16. Accordingly, FIG. 5 is an overview of ageneralized imaging system 66 that may be used in conjunction with themagnetoresistance sensors 16. The imaging system 66 may include theimager 42, the system control circuitry 46, the power circuitry 58, themonitor 64, and the user interface 65 as described above with respect toFIG. 4. However, rather than the antennas 60 and the receiver circuitry62, the imaging system 66 includes an external magnetic field generator68 (e.g., electromagnetic transmitter). The external magnetic fieldgenerator 68 may generate an alternating current (AC) or pulsed directcurrent (DC) magnetic field. The magnetoresistance sensors 16 generatesignals representative of location data (including position and/ororientation data) in response to the applied magnetic field, which maybe sent via the wires 56 to the system control circuitry 46 (inparticular the data processing circuitry 52). As discussed in moredetail below, the location data may be used in conjunction with theimage data to facilitate an image-guided procedure. The processed imagedata and/or location data may be forward to display circuitry 63 fordisplay at the monitor 64 for viewing and analysis.

To discuss the technique in greater detail, a specific medical imagingmodality based generally upon the overall system architecture outlinedin FIG. 4 is depicted in FIG. 6, which generally represents an X-raybased system 70. It should be noted that, while reference is made inFIG. 6 to an X-ray based system, the present technique also encompassesother imaging modalities, as discussed above, such as MRI, PET, SPECT,ultrasound, and so forth.

In the depicted exemplary embodiment, FIG. 6 illustratesdiagrammatically an X-ray based imaging system 70 for acquiring andprocessing image data. In the illustrated embodiment, imaging system 70is a computed tomography (CT) system or three-dimensional fluoroscopyimaging system designed to acquire X-ray projection data, to reconstructthe projection data into a two or three-dimensional image, and toprocess the image for display and analysis in accordance with thepresent technique. In the embodiment illustrated in FIG. 6, X-ray basedimaging system 70 includes a source of X-ray radiation 72 positionedadjacent to a collimator 74. The X-ray source 72 may be a standard X-raytube or one or more solid-sate X-ray emitters.

In the depicted embodiment, the collimator 74 permits a stream ofradiation 76 to pass into a region in which a subject, such as thepatient 44 is positioned. The stream of radiation 76 may be generallyfan or cone shaped, depending on the configuration of the detector arrayas well as the desired method of data acquisition. A portion of theradiation 78 passes through or around the patient 44 and impacts adetector array, represented generally as reference numeral 80. Detectorelements of the array produce electrical signals that represent theintensity of the incident X-ray beam. The signals generated by thedetector array 80 may be subsequently processed to reconstruct a visualrepresentation (i.e., an image or volumetric representation) of thefeatures within the patient 44. For example, images of the internalorgan 54 may be reconstructed in the depicted embodiment.

A variety of configurations of the detector 80 may be employed inconjunction with the techniques described herein. For example, thedetector 80 may be a multi-row detector, such as a detector having eightor sixteen rows of detector elements, which achieves limitedlongitudinal coverage of the object or patient being scanned. Similarly,the detector 80 may be an area detector, such as a high-resolutionradiographic detector having hundreds of rows of detector elements,which allows positioning of the entire object or organ being imagedwithin the field of view of the system 70. Regardless of theconfiguration, the detector 80 enables acquisition and/or measurement ofthe data used in image reconstruction of the internal organ 54.

The source 72 is controlled by a system controller 84, which furnishesboth power, and control signals for examination procedures. Moreover,the detector 80 is coupled to the system controller 84, which commandsacquisition of the signals generated in the detector 80. The systemcontroller 84 may also execute various signal processing and filtrationfunctions, such as for initial adjustment of dynamic ranges,interleaving of digital image data, and so forth. In general, systemcontroller 84 commands operation of the imaging system 70 to executeexamination protocols and to process acquired data. In the presentcontext, system controller 84 also includes signal processing circuitry,typically based upon a general purpose or application-specific digitalcomputer, associated memory circuitry for storing programs and routinesexecuted by the computer (such as programs and routines for implementingthe present technique), as well as configuration parameters and imagedata, interface circuits, and so forth.

In the embodiment illustrated in FIG. 6, the system controller 84 iscoupled to a linear positioning subsystem 86 and rotational subsystem88. The rotational subsystem 88 enables the X-ray source 72, collimator74 and the detector 80 to be rotated one or multiple turns around thepatient 44. It should be noted that the rotational subsystem 88 mightinclude a gantry or C-arm apparatus. Thus, the system controller 84 maybe utilized to operate the gantry or C-arm. The linear positioningsubsystem 86 typically enables a patient support, such as a table, uponwhich the patient rests, to be displaced linearly. Thus, the patienttable may be linearly moved relative to the gantry or C-arm to generateimages of particular areas of the patient 44.

Additionally, the source 72 of radiation may be controlled by an X-raycontroller 90 disposed within the system controller 84. Particularly,the X-ray controller 90 may be configured to provide power and timingsignals to the X-ray source 72. A motor controller 92 may also be partof the system controller 84 and may be utilized to control the movementof the rotational subsystem 88 and the linear positioning subsystem 86.

Further, the system controller 84 is also illustrated as including animage data acquisition system 94. In this exemplary embodiment, thedetector 80 is coupled to the system controller 84, and moreparticularly to the image data acquisition system 94. The image dataacquisition system 94 receives data collected by readout electronics ofthe detector 80. The image data acquisition system 94 typically receivessampled analog signals from the detector 90 and converts the data todigital signals for subsequent processing by processing circuitry 96,which may, for example, be one or more processors of a general orapplication specific computer.

As depicted, the system controller 84 also includes aposition/orientation data acquisition system 100 configured to acquireposition and orientation data from one or more antennas 102. In thedepicted embodiment, the one or more antennas 102 detect signals and/orfields generated by sensor elements 16 (e.g., electromagnetic sensors)on an interventional device 10 placed on or in the internal organ 54undergoing imaging or in the vasculature associated with the internalorgan 54. The position/orientation data acquisition system 100 processessignals acquired from the antennas 102 to generate position and/ororientation information about the interventional device 10 which isrepresentative of the internal organ 54 or of vasculature associatedwith the internal organ 54. The position and/or orientation informationgenerated by the position/orientation data acquisition system 100 may beprovided to the processing circuitry 96 and/or a memory 98 forsubsequent processing.

The processing circuitry 96 is typically coupled to the systemcontroller 84. The data collected by the image data acquisition system94 and/or by the position/orientation data acquisition system 100 may betransmitted to the processing circuitry 96 for subsequent processing andvisual reconstruction. The processing circuitry 96 may include (or maycommunicate with) a memory 98 that can store data processed by theprocessing circuitry 96 or data to be processed by the processingcircuitry 96. It should be understood that any type of computeraccessible memory device capable of storing the desired amount of dataand/or code may be utilized by such an exemplary system 70. Moreover,the memory 98 may include one or more memory devices, such as magneticor optical devices, of similar or different types, which may be localand/or remote to the system 70. The memory 98 may store data, processingparameters, and/or computer programs having one or more routines forperforming the processes described herein.

The processing circuitry 96 may be adapted to control features enabledby the system controller 84, i.e., scanning operations and dataacquisition. For example, the processing circuitry 96 may be configuredto receive commands and scanning parameters from an operator via anoperator interface 106 typically equipped with a keyboard and otherinput devices (not shown). An operator may thereby control the system 70via the input devices. A display 108 coupled to the operator interface106 may be utilized to observe a reconstructed visual representation.Additionally, the reconstructed image may also be printed by a printer110, which may be coupled to the operator interface 106. As will beappreciated, one or more operator interfaces 106 may be linked to thesystem 70 for outputting system parameters, requesting examinations,viewing images, and so forth. In general, displays, printers,workstations, and similar devices supplied within the system may belocal to the data acquisition components, or may be remote from thesecomponents, such as elsewhere within an institution or hospital, or inan entirely different location, linked to the image acquisition systemvia one or more configurable networks, such as the Internet, virtualprivate networks, and so forth.

The processing circuitry 96 may also be coupled to a picture archivingand communications system (PACS) 112. Image data generated or processedby the processing circuitry 96 may be transmitted to and stored at thePACS 112 for subsequent processing or review. It should be noted thatPACS 112 might be coupled to a remote client 114, radiology departmentinformation system (RIS), hospital information system (HIS) or to aninternal or external network, so that others at different locations maygain access to the image data.

Additionally, a specific medical imaging modality based generally uponthe overall system architecture outlined in FIG. 5 is depicted in FIG.7, which generally represents an X-ray based imaging system 116. Itshould be noted that, while reference is made in FIG. 7 to an X-raybased system, the present technique also encompasses other imagingmodalities, as discussed above, such as MRI, PET, SPECT, ultrasound, andso forth. The imaging system 116 may generally operate as discussedabove with respect to FIG. 6. However, the position/orientation dataacquisition system 100 of the imaging system 116 may be configured toacquire position and orientation data from one or more magnetoresistancesensors 16 disposed on or in the interventional device 10 and/or thesurgical tool (e.g., biopsy needle 26), when the magnetoresistancesensors 16 are exposed to an applied magnetic field. Accordingly, theimaging system 116 includes an external magnetic field generator 118(e.g., electromagnetic transmitter), which may be controlled by thesystem controller 84. The position/orientation data acquisition system100 processes data acquired from the magnetoresistance sensors 16 togenerate position and/or orientation information about themagnetoresistance sensors 14 of the interventional device 10 and/or thebiopsy needle 26. The position and/or orientation information generatedby the position/orientation data acquisition system 100 may be providedto the processing circuitry 96 and/or a memory 98 for subsequentprocessing.

The systems and devices described above may be utilized, as describedherein, to provide dynamic referencing for a region of a patientundergoing an interventional procedure. In an exemplary embodiment,dynamically acquired position and orientation data for the region of thepatient may be acquired using the interventional device 10 and sensorelements 16 and this data may be automatically registered withconcurrently or previously acquired image data without the use ofanatomical or fiducial markers. In this way, the interventionalprocedure may be performed or guided based upon the dynamicallyreferenced visual representation.

For example, referring to FIG. 8, examples of acts corresponding to oneimplementation of the present technique are provided. In theimplementation depicted in FIG. 8, the image data 122 is acquired (Block120) prior to the invasive procedure. As noted above, the image data 122may be acquired using one or more suitable imaging modalities, such asthree-dimensional fluoroscopy, CT, MRI, and so forth. In the depictedembodiment, the image data 122 is used to generate (Block 124) one ormore visual representations, such as images or volumes 126, of theinternal organ 54 (see FIG. 2) or and/or associated vasculature. In oneembodiment, the image data 122 is acquired after introduction of acontrast agent to the patient's bloodstream, thereby providing goodcontrast for the vasculature in the image data 122.

The images or volumes 126 are segmented (Block 128) in the depictedimplementation to provide one or more segmented regions 130. Such asegmentation process typically identifies pixels or those portions of animage representing common structures, such as organs, tissues,vasculature, and so forth. For example, a segmentation a process mayidentify surfaces or boundaries defining an organ, tissue, or bloodvessel (such as by changes in intensity or some other thresholdcriteria). In this way, all of those pixels representing respectiveorgans, tissues or blood vessels, portions of such organs, tissues orblood vessels, or regions proximate or connected to such organs,tissues, or blood vessels, may be identified and distinguished from oneanother, allowing processing or evaluation of only the portions of animage associated with the organs, tissues, or blood vessels of interest.For example, in an embodiment where contrast agents are employed and theliver and hepatic vasculature are the region of interest, the hepaticvein can be segmented in the images and/or volumes 126. In this manner,a geometric or spatial model of the segmented hepatic vein can begenerated for subsequent procedures, as described below.

The images or volumes 126 may be segmented using known segmentationtechniques, such as intensity and/or volume thresholding, connectivityclustering, and so forth. In one embodiment, the segmentation allows theorgan, tissue, blood vessel, or other region of interest to begeometrically or spatially modeled, as noted above. In an exemplaryembodiment, the segmented region corresponds to the internal organ 54 orblood vessel within which the interventional device 10 (see FIGS. 1 and2) will be placed for dynamic referencing. While the depicted actionsdescribe an embodiment in which images or volume 126 generated from theacquired image data 122 are segmented, in other embodiments thesegmentation may be performed on the image data 122 itself, with thesegmented image data being subsequently used to generate images orvolume of the internal organ 54, blood vessel, or other region ofinterest. Based upon the segmented image or volume of the internal organor blood vessel, i.e., the segmented region 130, a model 134 of theregion is generated (Block 132) which generally corresponds to theinternal organ 54, blood vessel, or other region of interest asdeterminable form the imaging process.

In some embodiments, the region model 134 may incorporate image dataacquired using more than one type of imaging modality. For example, insome embodiments, it may be desirable to use image data derived formboth an MRI system and an X-ray based imaging system, such as athree-dimensional fluoroscopy system. In such an embodiment, the signalsacquired by both system may be registered, as discussed below, such thatthe combined images and/or volumes 126, segmented region 130 and/orregion model 134 consists of or is representative of the imageinformation acquired by each imaging modality.

During the invasive procedure performed on the internal organ 54 (orother region of interest), the interventional device 10 is placed (Block140) in, on, or near the internal organ 54, such as in the vasculatureleading to the internal organ 54. As noted above, the interventionaldevice 10 includes at least three sensor elements 16, which in oneembodiment, are provided on a reference portion 14 of the interventionaldevice 10. The sensor elements 16 generate respective signals (such asrespective EM fields) which may be acquired (Block 142) or measured toderive position and/or orientation data 144 for each respective sensorelement 16. The position and/or orientation data 144 may be used togenerate (Block 146) a device model 148 representing shape, positionand/or orientation of the interventional device 10.

The device model 148 derived from the position and/or orientation data144 is registered (block 150) with the region model 134 generated usingthe imaging process. In one embodiment, the registration of the devicemodel 148 and the region model 134 is accomplished automatically, suchas using iterative closest point techniques. In this manner, the sensorelements 16 of the interventional device 10 are automatically registeredto the images of the region of interest, i.e., the internal organ 54and/or associated vasculature, thereby allowing the position and/ororientation of the internal organ 54 or associated vasculature to bemodified in a visual representation based on the most recent positionand/or orientation data from the sensor elements 16 of theinterventional device.

An image-guided invasive procedure may be performed using the registereddevice model 148 (based on the position and/or orientation data) andregion model 134 (based on the image data). In particular, once thepreviously acquired image-based information or model is registered tothe measured position and/or orientation data, changes in the positionand/or orientation data can be used to visually indicate changes to theimage-based model. In other words, a displayed image of the internalorgan 54 or the associated vasculature may be updated, modified,altered, or otherwise, changed, based on the most current positionand/or orientation data obtained from the sensor elements 16 of theinterventional device 10. In this way, even though no imaging processesare occurring during the operation, the previously acquired image datacan be updated and manipulated to provide an accurate and currentrepresentation of the internal organ and/or associated vasculatureundergoing the procedure.

Based on this registration between the region model 134 (derived theimage data) and device model 148 (derived from the sensor element data),an interventional tool may be tracked (Block 152) during aninterventional procedure. Examples of such interventional tools that maybe tracked include biopsy needles, catheters, ablation needles, and soforth. Typically the interventional tool being tracked also includes asensor element 16, such as an electromagnetic or magnetoresistancesensor, so that position and/or orientation information for theinterventional tool is also acquired, thereby allowing the position ofthe interventional tool to be displayed in conjunction with theregistered image of the moving and/or deformed internal organ 54 or thevasculature of such an organ. In this manner, a system such as thosedescribed herein, may display to a user in real-time or substantiallyreal-time the location of the interventional device relative to themoving and/or deformed internal organ 54 or its vasculature.

While the preceding described an implementation in which the imagingprocedure is performed prior to the interventional procedure, in otherimplementations the imaging procedure is performed concurrently with theinterventional procedure. For example, referring to FIG. 9, actsassociated with a further exemplary embodiment of the present techniqueare depicted. In this embodiment, a reference portion 14 of aninterventional device 10 is placed (Block 156) in or near an internalorgan 54 of interest, such as the vasculature leading to the internalorgan 54. Position and/or orientation data 160 is acquired (Block 158)for the sensor elements 16 integrated on the reference portion 14. Forexample, in embodiments where the sensor elements 16 generate EM signalsor fields, these signals or fields can be detected and/or measured, suchas using one or more antenna arrays as described above, to derive aposition and/or orientation for each respective sensor element 16.

In the depicted embodiment, image data 122 is acquired (Block 120) andis used to generate (Block 124) one or more images and/or volumes 126.Some or all of the sensor elements 16 are located (Block 162) in theimages and/or volumes 126 such that the position data 164 for therespective sensor elements 16 is obtained with respect to theimages/volumes 126. In an exemplary embodiment, the sensor elements 16are automatically located in the images/volumes 126. For example, thesensor elements 16 may be automatically located using image processingtechniques such as intensity and/or volume thresholding, connectivityclustering, template matching, and so forth. In addition, in someembodiments, the positions of the sensor elements 16 are known withrespect to one another based on the measured signals or fields generatedby the sensor elements 16. This sensor derived position data 158 may beused to find the sensor elements 16 in the images and/or volumes 126.

Once some or all of the sensor elements 16 are identified in the imagesand/or volumes, the positions 164 of the sensor elements 16 located inthe images and/or volumes may be matched (Block 166) to thecorresponding sensor element locations as determined from the sensorposition data 160. In other words, the sensor elements 16 located in theimages and/or volumes are matched with the corresponding sensor elementssignals and/or fields generated by the sensor elements 16. In oneembodiment, this may be facilitated by using different sizes of sensorelements 16 on the interventional device 10 such that the sensorelements 16 can be distinguished in the image data and matched to theircorresponding sensor signals. Likewise, a priori information aboutpatient position in the images may be used to determine which sensorelement 16 is the element and which is the proximal one, therebyallowing matching between the sensor element readings and the identifiedsensor elements 16 in the images. Alternatively, a sufficiently largenumber (i.e., four or more) of sensor elements 16 may be provided in oneembodiment such that all possible matches may be permuted and the matchgenerating the smallest registration error is selected as the correctmatch or correspondence.

Based on the established or possible correspondences, the sensor elementpositions derived using the sensor data and the imaging data areregistered (Block 168). As noted above, in some embodiments, theregistration and the establishment of the correspondences may actuallydepend on one another, i.e., the registration errors associated withdifferent possible matches may be used to select the correctcorrespondence. In one embodiment the centroid of each sensor element 16as determined in the images and/or volumes is registered to thecorresponding sensor element signal in the position data derived fromthe sensor elements 16. In certain implementations the registration canbe accomplished using iterative optimization techniques or a closed formsolution. As noted above, in certain embodiments, to obtain a uniqueregistration it is generally desired that the three or more sensorelements not lie on or near a straight line. In certain embodiments,such as in an embodiment where the interventional device 10 is acatheter configured for insertion into the hepatic artery, theinterventional device may be designed so that the sensor elements 16 arestructurally prevented from being collinear, i.e., the reference portion14 may be curved. In other embodiments, such as where the sensorelements 16 are not structurally prevented from being collinear,feedback may be provided to the user in the event that a uniqueregistration can not be determined and the user can adjust the positionof the interventional device 10 until a unique registration is obtained.

Once the sensor elements 16 are registered in both the sensor space(such as EM space) and the image space, the interventional procedure maybe performed using the dynamic tracking of the internal organ based uponthe signals from the sensor elements 16. For example, no further imagingmay be performed or the image data may be updated only sporadically,with other updates to the images used in the interventional procedurebeing based upon the continuous, substantially real-time tracking of thesensor elements 16. In this way, even though imaging does not occur oroccurs only sporadically during the operation, the displayed images canbe updated and manipulated to provide an accurate and currentrepresentation of the internal organ 54 (or other internal region)undergoing the procedure.

In one implementation an interventional tool may be tracked (Block 152)during an interventional procedure, using images updated based upon theposition data derived form the sensor elements and the registration ofthese signals with the image and/or volumes 126. Examples of suchinterventional tools that may be tracked include biopsy needles,catheters, ablation needles, and so forth. Typically the interventionaltool being tracked also includes a sensor element 16, such as an EMsensor, so that position and/or orientation information for theinterventional tool is also acquired, thereby allowing the position ofthe interventional tool to be displayed in conjunction with the imageupdated using the position data for the sensor elements 16. In thismanner, a system such as those described herein, may display to a userin real-time or substantially real-time the location of theinterventional tool relative to the moving and/or deformed internalorgan 54.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

The invention claimed is:
 1. A tracking system comprising: aninterventional tool including a proximal region that remains outside apatient and a terminal region that is suitable for insertion into thepatient and placement proximate to or inside an internal organ of thepatient, said interventional tool comprising: a reference portion thatis disposed in said terminal region, wherein the reference portion isnot physically attached to the internal organ when so placed; two ormore electromagnetic coils integrated on the reference portion of theinterventional tool, wherein each of the two or more electromagneticcoils is configured to provide at least position information, whereineach electromagnetic coil of the two or more electromagnetic coils iseither sized differently so as to be identifiable in a radiographicimage or the two or more electromagnetic coils are positioned so as tobe identifiable in the radiographic image based, at least in part, upontheir known spatial relationship to one another; and a controllercomprising processing circuitry operatively coupled to memory circuitry,wherein the processing circuitry is configured to execute instructionsstored on the memory circuitry to cause the processing circuitry toreceive the position information generated by the two or moreelectromagnetic coils and to register the two or more electromagneticcoils to the corresponding position information in the radiographicimage of the internal organ based, at least in part, upon either thesize differences or known spatial relationship between the two or moreelectromagnetic coils.
 2. The tracking system of claim 1 wherein theinterventional device comprises a or a biopsy needle catheter.
 3. Thetracking system of claim 1 comprising one or more antennas configured todetect electromagnetic fields generated by the two or moreelectromagnetic coils.
 4. The tracking system of claim 1 wherein eachelectromagnetic coil provides position information in three dimensionsand orientation information in two directions.
 5. The tracking system ofclaim 1 comprising at least one imaging modality configured to generatethe radiographic image of the internal organ.
 6. The tracking system ofclaim 1 wherein the processing circuitry is configured to executeinstructions stored on the memory circuitry to cause the processingcircuitry to track the interventional tool using at least the registeredposition information and the radiographic image of the internal organ.7. The tracking system of claim 1 wherein the two more electromagneticcoils of the interventional tool are arranged in a non-lineararrangement on a curved portion of the interventional tool.
 8. Thetracking system of claim 7 comprising one or more antennas configured todetect electromagnetic fields generated by the two or moreelectromagnetic coils.
 9. The tracking system of claim 1 wherein eachelectromagnetic coil of the two or more electromagnetic coils is sizeddifferently so as to be identifiable in a radiographic image.
 10. Thetracking system of claim 1 wherein each electromagnetic coil of the twoor more electromagnetic coils are positioned so as to be identifiable inthe radiographic image based, at least in part, upon their known spatialrelationship to one another.
 11. A tracking system comprising: aninterventional tool including a proximal region that remains outside apatient and a terminal region that is suitable for insertion into thepatient and placement proximate to or inside an internal organ of thepatient, said interventional tool comprising: a reference portion; twoor more electromagnetic coils integrated on the reference portion of theinterventional tool, wherein each coil of the two or moreelectromagnetic coils is configured to provide at least positioninformation, wherein each coil of the two or more electromagnetic coilsis either sized differently so as to be identifiable in a radiographicimage or the two or more electromagnetic coils are positioned so as tobe identifiable in the radiographic image based, at least in part, upontheir known spatial relationship to one another; and a controllercomprising processing circuitry operatively coupled to memory circuitry,wherein the processing circuitry is configured to execute instructionsstored on the memory circuitry to cause the processing circuitry toreceive the position information generated by the two or moreelectromagnetic coils and to register the two or more electromagneticcoils to the corresponding position information in the radiographicimage of the internal organ based, at least in part, upon either thesize differences or known spatial relationship between the two or moreelectromagnetic coils.